TIJ technology is widely used in computer printers. Very generally, a TIJ includes a print head typically comprising several tiny controllable ink-jets, which are selectively activated to release a jet or spray of ink from an ink reservoir onto the print media (such as paper) in order to create an image or portion of an image. TIJ printers are described, for example, in the Hewlett-Packard Journal, Volume 36, Number 5, May, 1985, and Volume 39, Number 4, August, 1988.
Thermal ink-jet print cartridges operate by rapidly heating a small volume of ink to cause the ink to vaporize and be ejected through one of a plurality of orifices so as to print a dot of ink on the print medium. Typically the orifices are arranged in one or more linear arrays in a nozzle member. The properly sequenced ejection of ink from each orifice causes characters or other images to be printed upon the paper as the printhead is moved relative to the paper.
In one known design, the ink-jet printhead generally includes ink channels to supply ink from an ink reservoir to each vaporization chamber proximate to an orifice, a metal orifice plate or nozzle member in which the orifices are formed in the required pattern, and a silicon substrate containing a series of thin film resistors, one resistor per vaporization chamber.
To print a single dot of ink, an electrical current from an external power supply is passed through a selected thin film resistor. The resistor is then heated, in turn superheating a thin layer of the adjacent ink within a vaporization chamber, causing explosive vaporization, and consequently, causing a droplet of ink to be ejected through an associated orifice onto the paper.
An exemplary ink-jet cartridge is described in U.S. Pat. No. 4,500,895, entitled "Disposable Inkjet Head," and assigned to present assignee.
Another ink-jet printhead is described in U.S. Pat. No. 4,683,481, entitled "Thermal Ink Jet Common-slotted Ink Feed Printhead," ink is fed from an ink reservoir to the various vaporization chambers through an elongated hole formed in the substrate. The ink then flows to a manifold area, formed in a barrier layer between the substrate and a nozzle member, then into a plurality of ink channels, and finally into the various vaporization chambers. This design is known as a center feed design, whereby ink is fed to the vaporization chambers from a central location and then distributed outwardly into the vaporization chambers.
Commonly assigned U.S. Pat. No. 5,278,584, entitled "Ink Delivery System for an Inkjet Printhead," describes an edge feed printhead design. A barrier layer containing ink channels and vaporization chambers is located between a rectangular substrate and a nozzle member containing an array of orifices. The substrate contains two linear arrays of heater elements, and each orifice in the nozzle member is associated with a vaporization chamber and heater element. The ink channels in the barrier layer have ink entrances generally running along two opposite edges of the substrate so that ink flowing around the edges of the substrate gain access to the ink channels and to the vaporization chambers.
In TIJ pens it is necessary to connect the ink reservoir to the print head. The size of this connection affects the design of the printer that the pens are used in. An ideal reservoir-to-print-head coupler, from a print design point of view, would be no longer than the TIJ head is long, and would be high or tall enough to allow the drive and pinch wheels to get as close to the print head as possible. Any increase in the size of this coupler will compromise the paper handling ability, which may affect the print quality, and increase the size of the printer.
An intended application for this invention is for a spring bag ink-jet pen, although it is not limited to the spring bag pen. In one exemplary spring bag pen design, the pen frame made of a first molded material is lined with a second molded material, such as polyethylene, on the inside to produce a surface suitable for staking the films of the spring bag. The first molded material from which the frame is made could be, for example, an engineering plastic, and provides the necessary structure for the pen which could not be accomplished with the second molded material. This invention relates to the fluid connection of the first and second molded materials in such a way as to provide a space-efficient, leak-resistant connection.
Conventional methods of connecting materials include the use of glue, seals, such as gaskets or O-rings, or mechanical press fits. In these cases two or more separate parts are fabricated and assembled together to form a single unit. Each part must be designed and sized with respect to its needs in manufacturing, structural integrity, and with the tolerance of the mating part in mind. Such joints as these take up space, and their reliability can be affected by the part tolerances, surface finishes, and the assembly operation.
Commonly assigned pending application Ser. No. 07/853,372 now U.S. Pat. No. 5,464,578 describes a leak-resistant joint between the first and second molded materials, wherein the second molded material has a shrink rate as the material cools from a molten state, so that the second molded material molded about a standpipe formed of the first molded material will shrink, thereby creating a tight joint between the two molded materials.